Catalytic hydrocarbon cracking is a major process commercially practiced, e.g., by petroleum refiners, to produce gasoline and other relatively low boiling hydrocarbon products. Such cracking often occurs in the presence of solid particles containing zeolite-containing cracking catalyst. In most conventional catalytic cracking processes in which hydrocarbon feedstocks are cracked to produce gasoline and other light distillates, a gradual deterioration in the cracking ability or performance of the molecular sieve-containing catalyst occurs. At least a part of the deterioration is often attributable to the deposition on the solid particles of contaminant metal or metals from the feedstock. The deposition of these contaminants, which include nickel, vanadium and iron, tends to adversely affect the cracking process, for example, by decreasing gasoline production and undesirably increasing the yields of hydrogen and coke.
Vanadium is of particular concern since vanadium oxide or vanadia can penetrate the structure of the molecular sieve and interact to form low melting eutetics that lead to neutralization of acid sites and irreversible destruction of molecular sieve crystallinity, producing a less active, lower surface area amorphorous material.
A number of attempts have been made to mitigate against the deposition of such contaminant metals on solid cracking catalyst particles. For example, a number of U.S. patents to Phillips Petroleum Company disclose the use of antimony as a nickel passivation agent. Certain U.S. patents to Gulf Oil Corporation disclose the use of tin as a metals passivation agent. U.S. Pat. No. 4,451,355 to Gulf Oil Corporation discloses the use of calcium-titanium, calcium-zirconium and calcium titanium-zirconium oxides and mixtures thereof as additives for a catalyst useful for cracking a vanadium-containing hydrocarbonaceous oil. A large number of other passivating metal components have been suggested, for example, gallium, indium, zinc, tellurium, aluminum, cadmium and arsenic. See: U.S. Pat. Nos. 4,324,648; 4,348,273; 4,504,381; 4,415,440; 4,167,471; 4,363,720; 4,326,990; and 4,396,496.
The use of various barium compounds to passivate contaminating metals on hydrocarbon cracking catalysts is disclosed in U.S. Pat. Nos. 4,473,463; and 4,377,494. These patents teach that the useful barium compounds can be organic or inorganic, with oil or water soluble barium compounds being preferred. Suitable inorganic barium compounds include barium salts of mineral acids such as barium nitrate, barium sulfate, barium halides and barium oxyhalides; and basic barium compounds such as barium hydroxide, barium hydrosulfide and barium carbonate. European patent publication No. 0 194 536 discloses the use of barium titanium oxide, in particular barium titanate, in combination with zeolitic molecular sieve cracking catalyst for cracking metal-containing hydrocarbon feedstocks.
U.S. Pat. No. 4,432,890 discloses a number of metal additives for immobilizing vanadia on zeolite-containing cracking catalysts. Such metal additives include the following metals, their oxide and salts and their organo-metallic compounds: Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zn, Hf, Nb, Ta, Mn, Fe, In, Tl, Bi Te, the rare earths, and the actinide and lanthanide series of elements. This patent recognizes that mixtures of these additive metals, other than the Group IIA or alkaline earth metals, e.g., Mg, Ca, Sr and Ba, with vanadia may occur to form high melting ternary, quaternary or higher component reaction mixtures, such as vanadium titanium zirconate (VO--TiO.sub.2 --ZiO.sub.2). This patent also states that although Group IIA metals and other metals are capable of tying up vanadia in high melting immobile materials, such as Ba.sub.3 VTi.sub.2 O.sub.9, BaO--K.sub.2 O--TiO.sub.2 --V.sub.2 O.sub.4, and BaO--Na.sub.2 O--TiO.sub.2 --V.sub.2 O.sub.5, those metals may result in excessive neutralization of acidic sites on the catalyst and generally are not used as metal additives for immobilizing vanadia on zeolite-containing cracking catalysts.
However, there continues to be a need for metals, in particular vanadium, passivating agents for zeolite-containing cracking catalyst.
The following additional U.S. Pat. Nos. were reviewed during the preparation of this application: 3,446,730; 4,450,241; 4,425,259; 4,412,914; 4,149,998; 4,418,008; 4,089,810; 4,293,445; 3,360,330; and 3,317,439.